Rotational mechanism

ABSTRACT

A rotational mechanism is used, e.g., in a vacuum deposition apparatus, for suspending a substrate holder above its stationary supports for rotation free of any bearings within a heated portion of a vacuum chamber. At the beginning of the vacuum deposition cycle a shaft in the rotational mechanism is rotated to enable the mechanism to engage the substrate holder and lift it above its stationary supports due to inertia of the substrate holder. The substrate holder is then rotated during the vacuum deposition, after which the direction of rotation of the shaft is reversed, and the substrate holder is lowered onto its support member, again due to inertia, thus eliminating bearing contact among the rotational mechanism, the substrate holder, and the stationary supports during the vacuum deposition.

Unite States Patent Phinlney [451 Feb. 29, 1972 [54] ROTATIONALMECHANISM [72] Inventor: Richard R. Phinney, Milton, Vt.

[73] Assignee: International Business Machines Corporation, Armonk, N.Y.

[22] Filed: Aug. 13, 1970 [21] Appl. No.: 63,351

Richison et al. ..l92/94 X Primary Examiner-Morris Kaplan AttorneyI-Ianifin and Jancin [57] ABSTRACT A rotational mechanism isused, e.g,, in a vacuum deposition apparatus, for suspending a substrateholder above its stationary supports for rotation free of any bearingswithin a heated portion of a vacuum chamber. At the beginning of thevacuum deposition cycle a shaft in the rotational mechanism is rotatedto enable the mechanism to engage the substrate holder and lift it aboveits stationary supports due to inertia of the substrate holder. Thesubstrate holder is then rotated during the vacuum deposition, afterwhich the direction of rotation of the shaft is reversed, and thesubstrate holder is lowered onto its support member, again due toinertia, thus eliminating bearing contact among the rotationalmechanism, the substrate holder, and the stationary supports during thevacuum deposition.

14 Claims, 3 Drawing Figures ROTATIONAL MECHANISM BACKGROUND OF THEINVENTION 1. FIELD OF THE INVENTION The invention relates to the fieldof rotational systems adapted for use within, e.g., vacuum environmentsand more particularly to rotational systems for use within vacuumdeposition systems. More particularly, it relates to a rotationmechanism in which inertia of a member to be rotated is utilized toraise and lower the member with respect to stationary supports.

2. DESCRIPTION OF THE PRIOR ART In the semiconductor industry manydepositions are performed in vacuum. These depositions are of varyingmaterials, but often involve vacuum evaporation of metals to forminterconnection metallurgy on integrated circuits. The depositionmaterial is deposited on relatively large silicon wafer substratescontaining many individual integrated circuits. In order to producedeposits with the desired characteristics it is generally necessary toheat the substrates as well as the source of the deposition material.Because of the time and costly equipment involved, it is common practiceto process many substrates at one time.

In order to obtain deposits having a uniform thickness over eachsubstrate and of the same thickness from one substrate to another, it isthe general practice to mount the substances on a large substrate holderwhich is rotated during the deposition process. The rotation of thesubstrate holder provides even deposition over all substrates from amuch smaller and more controllable deposition source than would bepossible without the rotation. However, the rotation of the substrateholder is not without problems.

Because of the high heat required for proper vacuum evaporation, andcontamination of bearings by the deposition material, bearings withinthe vacuum chamber for subject to a rapid wear rate and a consequentshort lifetime. Because of the rapid wear rate, excessive maintenance isrequired to maintain system operation.

Although reduced bearing life is a problem, a more serious problem isthe introduction of contaminating impurities into the integratedcircuits. If the bearings are not lubricated, the heat and vacuumconditions quickly lead to particles being rubbed off the bearings.These particles in contact with the substrates form impurities in theintegrated circuits. If the bearings are lubricated to prevent bearingwear, then the lubricant evaporates under the high heat and vacuumconditions and deposits on the substrates as a contaminating impuritv.

For these reasons, bearing wear and contamination present seriousquality control problems, as well as being significant factors in thecost of maintaining production equipment in usable condition.

OBJECTS A primary object of the present invention is to enable uniformvacuum deposition to be performed in an uncontaminated environmentwithout requiring frequent maintenance of the vacuum deposition system.

Another object of the invention is to improve the manner of supporting arotatable substrate holder so as to result in substantially no wear,without the introduction of contaminating lubricants.

Still another object of the invention is to provide a mechanism forrotating a member which will raise the member to be rotated fromstationary supports as a result of the inertia ofthe member to berotated.

Yet another object of the invention is to eliminate bearing contact inall heated areas of a vacuum deposition apparatus in which a substrateholder is rotated.

SUMMARY The above objects are accomplished by providing a novelsuspension and rotation or pickup mechanism as described herein. As inprior art systems a vacuum chamber contains a heated deposition sourceand means for heating the substrates for proper deposition. Thesubstrates are mounted on a substrate holder which rests on a stationarysupport means attached to the vacuum housing. The suspension androtation mechanism includes a rotatable housing mounted within thevacuum chamber and connected by a shaft to a suitable rotational drivemeans. A retraction means responsive to the inertia of the substrateholder is coupled to the rotatable housing. A releasable latch means hasa latch member attached to the retraction means and an engaging memberattached to the substrate holder. The retraction means provides foraxial movement of the latch member toward and away from the substrateholder support means.

The rotational mechanism is operated by rotating the shaft and housingto cause the releasable latch means to engage, thus coupling therotational mechanism to the substrate holder. Continued rotation of theshaft and the housing causes the retraction means to raise the substrateholder from its supports, due to the inertia of the substrate holder andfriction between the substrate holder and its supports while they arestill in contact. Once the inertia of the substrate support has beenovercome, it stops raising and rotates at the same speed as the shaftand housing. When it is no longer desired to rotate the substrateholder, the direction of rotation of the shaft and housing is reversed.Due to the rotational inertia of the rotating substrate holder, theretraction means lowers the substrate holder back onto its supports, andthe releasable latch means disengages to separate the rotationalmechanism and the substrate holder.

When the substrate holder is picked up and rotating at full speed, thereis no bearing contact among the rotational mechanism, the substrateholder, or the supports for the substrate holder. This makes therotational mechanism especially suited for use in a vacuum environment,where bearing contact is a problem. However, the rotational mechanismshould find application in a wide variety of other environments as well.

The above and other objects and advantages of the invention will beapparent from the following more particular description of the preferredembodiment of the invention, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial section of apreferred embodiment of the invention in perspective showing therotational mechanism in a vacuum deposition system prior to engagementwith a substrate holder;

FIG. 2 is a view of the rotational mechanism similar to FIG. 1, but withthe mechanism in the initial stage of engagement of the substrateholder; and

FIG. 3 is a view of the rotational mechanism as in FIG. 2, but with thesubstrate holder fully engaged and raised by the mechanism.

DETAILED DESCRIPTION A vacuum deposition system including a preferredembodiment of a rotational mechanism 130 are shown in partial sectionand perspective in FIG. I. A vacuum chamber is shown generally at and isused for performing the vacuum deposition process. Within the chamber isa support means 108 for supporting a substrate holder 300. Also mountedin the chamber is a deposition source 110 and a heating means 112 forheating substrates (not shown) mounted on substrate holder 300 to obtainproper deposition. The rotational mechanism is attached to shaft 128which is rotatably mounted through a vacuum seal or rotary feedthrough(not shown) in the top of the chamber 100 and is connected to suitabledrive means such as a motor (not shown). The function of drive shaft 128is to support and rotate the mechanism 130. The vacuum seal tightlygrips the shaft 128 to prevent leakage to the inside of the vacuumchamber 100. The seal is not subject to much load because the supportbearings i.e., the bearings which support the weight of the shaft andconstrain it to rotate about its axis, are outside the vacuum chamber.Thus, the seal is not subject to significant wear. The vacuum seal isthe only bearing surface contacting the inside of the vacuum chamber 100during rotation of the substrate holder 300, and it may be suitablyshielded to protect it from heat and to keep contaminants from it fromreaching substrates on the substrate holder 300.

The mechanism 130 has a generally cylindrical housing 140 rigidlymounted to the drive shaft 128. The housing 140 has a generallycylindrical cavity 145 within it.

A retraction means 165 is disposed in the cavity 145 for raising andlowering a releasable latch means 210. The retraction means includes anut 170 and a screw 190. The nut 170 is generally cylindrical in shapeexcept for a keyway 176 which engages key 152 mounted on the wall ofhousing 140 within cavity 145. The key and keyway forces the nut 170 torotate with housing 140, but allows the nut 170 to slide up and downinside the cavity 145. Bottom plate 154 disposed at the lower end ofcavity 145 acts as an abutment to prevent nut 170 from coming out of thecavity 145.

The nut has an inner threaded surface 172 which mates with an outerthreaded surface 192 of screw 190. The screw 190 has a reduced diametersection 194 slidably fitted in passageway 155 in bottom plate 154. Screw190 is dimensioned so that shoulder 200 of the screw will rest on bottomplate 154 when the screw is in the position shown.

Compression coil spring 290 is located in the cavity 145 and exertspressure between the top of the nut 170 and a surface 291 of housing 140at the top of cavity 145 at all times. Thus, the spring urges nut 170downward, assuring that shoulder 200 of screw 190 rests on bottom plate154 when the nut is backed up, so as to provide resistance to turningthe screw.

Releasable latch means 210 includes a rod 212 supported by andpositioned perpendicular to the axis of screw 190 and hook-shaped dogs214 on substrate 300 adapted to be engaged by rod 212 to couple therotational mechanism 130 to the substrate holder 300 which is to berotated.

A means for activating the releasable latch means 210 is provided by theretraction means 165, the housing 140, the substrate holder 300 and thespring 290. When shoulder 200 of screw 190 rests on bottom plate 154,the rod 212 and dogs 214 are in an engageable position. Rotation ofhousing 140 in a clockwise direction turns nut 170, which turns screw190 until the rod 212 strikes the dogs 214, as shown in FIG. 2, whichremain stationary because of the inertia of substrate holder 300 andfriction between it and its support means 108. The nut then continues toturn with housing 140 which raises the rod 212 into the hook portions ofdogs 214. Upon continued rotation of member 140 after engagement of rod212 and dogs 214, the substrate holder is raised from its support meansbecause the combination of continued friction between it and the supportmeans 108, and its inertia, prevents screw 190 from rotating with nut170, and screw 190 therefore moves upward within nut 170. Substrateholder 300 continues to be raised until its inertia is overcome and itis rotating at the same speed as housing 140, and screw 190 no longermoves upward within nut 170. The housing 140, retraction means 165, thereleasable locking means 210 and the substrate holder 300 now rotate asa single unit, in the position shown in FIG. 3.

In order to increase the efiective weight of the substrate holder 300prior to raising it, a lifting resistance means 230 is provided forresisting the lifting of the substrate holder 300 in order to assist inraising the substrate holder 300 to a precisely predetennined extenteach time it is raised. The lifting resistance means includes a bearing232, a spring 240, and a checking sleeve 250. The bearing 232 has anupper bearing member 234 mounted on the upper surface of housing 140.The upper bearing member 234 is attached to housing 140 so that it mustrotate at the same speed as the shaft 128 and the housing 140. Thebearing 232 has a lower bearing member 236 which is free to rotate withrespect to the housing 140 to that the spring 240 and checking sleeve250 will remain stationary with respect to the substrate holder 300 atall times. The spring 240 has its upper end pressing against the lowersurface of the lower bearing member 236 and its lower end pressingagainst the top of the checking sleeve 250. The checking sleeve 250 is ahollow stepped cylinder having a large diameter section 252 at thebottom and a reduced diameter section 254 at the top. The step forms alower shoulder 258 and an upper shoulder 260. The spring 240 presses onshoulder 260 at all times and shoulder 258 rests on outer supportshoulder 158 of housing 140 when the mechanism is not in contact withthe substrate holder. The reduced diameter cylindrical portion 254 isadjacent to the outer cylindrical surface of housing 140 and serves toguide checking sleeve 250 and to retain its vertical orientation. Thelower surface of section 252 of checking sleeve 250 presses against thesubstrate holder 300 to apply the lifting resistance to the substrateholder. The lifting resistance means 230, by constantly pressing down onthe substrate holder 300, assures that the releasable latch means 210will remain locked as long as substrate holder 300 is not resting onsupport means 108 and helps to determine the height to which thesubstrate holder is raised above support means 108.

Substrate holder 300 has a flat shape near its center and a thin domeshaped portion upon which the substrate holding locations (not shown)are arranged. Although the embodiment shown is dome shaped because ofthe pattern of the deposition source, it could be flat if the pattern ofthe deposition source required a flat surface.

OPERATION Succeeding stages in an operation cycle are shown in FIGS. 1through 3. The mechanism 130, mounted with shaft 128 through vacuumchamber 100, is adjusted by turning screw 190 so that its shoulder 200rests on plate 154 and rod 212 is positioned to clear dogs 214. FIG. 1shows the rotational mechanism 130 in contact with the substrate holder.As the chamber and the mechanism is lowered into the position shown inFIG. 1, the checking sleeve 250 makes contact along its lower surfacewith the substrate holder 300. Further lowering of the top of thehousing compresses spring 240 as the mechanism 130 is pressed downtoward the substrate holder. When fully lowered into engageablerelationship as shown in FIG. 1, the top of the rod 212 is lower thanthe hookshaped openings in the dogs 214 on the substrate holder 300.With the vacuum chamber 100 now in position, conventional vacuumdeposition pumpdown is carried out.

The drive means (not shown) is now started to rotate the drive shaft 128and the rotatable support member in a clockwise direction at a slowspeed, preferably at about 8 rpm. to preventjarring of the substrates.The checking sleeve 250, the spring 240 and the lower bearing member 236remain stationary with the substrate holder 300. Nut is constrained torotate with the housing 140 because of the key 152 and the keyway 176.As shown in FIG. 2, the screw turns with the nut 170 until the rod 212strikes the back of the opening in dogs 214. Once the rod 212 strikesthe dogs 214 the screw 190 stops turning because of the inertia of thesubstrate holder 300 and the friction between the substrate holder andits supports 108. Continued rotation of housing 140 turns the nut 170downward on the screw 190 until the nut 170 strikes bottom plate 154.Until nut 170 strikes bottom plate 154, a rotational force to screw 190is applied to assure that rod 212 remains firmly seated in dogs 214.

The check sleeve 250, the spring 240, and the lower bearing member 236now remain stationary, while the nut continues to advance on screw 190,thereby raising the screw 190 through nut 170, and therefore raising therod 212 up into the hook-shaped portion of the dogs 214, as shown inFIG. 2.

Referring to FIG. 3, once the rod 212 has fully engaged the dogs 214 thecontinued advance of the nut 170 on screw 190 raises the substrateholder 300 off support means 108.

Since the substrate holder is no longer in frictional contact withsupports 108 and the inertia of the substrate holder begins to decrease,the screw 190 will start to rotate with the nut 170. If the screwadvances, the substrate holder is lifted and if the screw turns with thenut, the substrate holder must also turn with the nut. The combinationof the weight of the substrate holder 300 and the force exerted throughchecking sleeve 250 by spring 240, resists the vertical movement of thesubstrate holder 300. Thus, the height to which the substrate holder israised depends on a combination of the strength of spring 240, and theinertia or weight of the substrate holder 300. Therefore, if a differentheight is desired, the strength of spring 240 is merely changed. As thescrew advances and raises the substrate holder, the substrate holdersrotational speed increases until it is the same as that of the housing140. When the substrate holder 300 reaches the speed of the housing thescrew will have stopped advancing and the entire pickup mechanismrotates as a single unit with the substrate holder. Vacuum depositionnow can take place.

If it is desired to do so, substrate holder 300 could be raised furtherfrom supports 108 than shown in FIG. 3 by merely increasing the rotationof shaft 128 from, for example 8 rpm, to 16 r.p.m. The rotationalinertia of substrate holder 300 would cause screw 190 to advance furtherin nut 170 until the rotation of substrate holder 300 again matched thatof shaft 128. After deposition has been completed, it is desired toreturn substrate holder 300 on supports 108. The drive means (not shown)for shaft 128 is reversed, preferably at a high speed such as 40 rpm.for a short time, such as one-half second, to start the screw 190lowering the substrate holder. The motor is then run backward at aslower speed, such as 8 r.p.m., until the nut is retracted and theapparatus returned to the position shown in FIG. 2. The particularspeeds depend on the characteristics of the spring 240 and are bestdetermined experimentally.

in further explaining what takes place when the motor is reversed,rotational inertia keeps the substrate holder 300 rotating in theforward direction when the motor is first reversed. Thus, screw 190starts downward toward supports 108. As the screw advances downwardly,the inertia of the substrate holder is overcome and it desirably stopsrotating just before it comes to rest on its supports 108.

While the motor is still running backward and after the substrate holderis resting on its supports as shown in FIG. 2 the screw 190 continues tomove downward until the rod 212 disengages from the dogs 214. After therod disengages from the dogs, the screw 190 turns until the rod 212strikes the back sides of the adjacent dogs. Once the rod 212 hits thebacks of the dogs 214, the screw stops turning and the screw advancesdownwards until its shoulder 200 rests on the bottom plate 154, as shownin FIG. 1. From there on, the nut 170 retracts upwards through thecavity 145 until the drive shaft 128 stops, thus providing lost motionto allow time to stop the motor.

Now, returning to the deceleration step in the deposition cycle, thesubstrate holder 300 is decelerated to return to its sup port means 108without rotational motion. This prevents jarring, scraping of thesupport means 108 or displacement ofthe substrates (not shown) on thesubstrate holder 300. The deceleration is accomplished by the reversedrive applied to the drive shaft 108. The reverse drive, combined withthe force applied by spring 240, determines the rate of deceleration ofthe substrate holder, and should be experimentally determined so thatthe substrate holder 300 is not rotating when returned to its supportmeans 108.

The entire engaging, lifting, lowering and disengaging operationsconsume a small proportion of the total time the system operates duringa vacuum deposition run, and is the only time that bearing contactexists in the rotational mechanism T30. These operations, as well asrotation of the dome when engaged and lifted, may therefore be carriedout under vacuum deposition conditions without causing substantial wearto the rotational mechanism. If desired, the engaging, lifting, loweringand disengaging operations may be carried out under atmosphericconditions, but this is not necessary.

This substrate holder pickup mechanism results in permitting a largenumber of runs to be performed before rebuilding of the depositionequipment becomes necessary. With the pickup device of the invention,700 production runs have been achieved without rebuilding the equipment,thereby representing a significant advance over other known vacuumdeposition systems.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention.

1 claim:

1. An article rotational mechanism comprising:

rotatable retraction means responsive to the inertia of an article to berotated to move the article to be rotated from an initial position, thento rotate the article, and

means for coupling the article to be rotated to said retrac' tion means.

2. The apparatus of claim 1 wherein the retraction means is a nut andscrew which are constrained to rotate with respect to one another by therotational inertia of the article to be rotated to move the article tobe rotated from the initial position, then which rotate together torotate the article.

3. The apparatus of claim 1 wherein said retraction means is responsiveto the rotational inertia of the rotating article when the article isrotating in a forward direction and a portion of the rotatableretraction means is rotating in a reverse direction so as to return thearticle to its initial position.

4. The apparatus of claim 1 wherein said means for coupling the articleto be rotated to said retraction means is releasable and comprises alatch member coupled to said retraction means and a means engageablewith said latch member coupled to the article to be rotated.

5. The apparatus of claim 1 additionally comprising: means tending torestrain the retraction of said rotatable retraction means.

6. An article suspension and rotation apparatus comprising:

a rotatable housing;

retraction means, responsive to the rotational inertia of an article tobe rotated which rests on a stationary support for the article from itssupport, coupled to said rotatable housing;

a latch member coupled to said retraction means; and

means, releasably engageable with said latch member, coupled to thearticle to be rotated.

7. The apparatus of claim 6 wherein the retraction means is a nut andscrew which are constrained to rotate with respect to one another by therotational inertia of the article to be rotated to move the article fromits support, then rotate together to rotate the article.

8. The apparatus of claim 7 wherein said retraction means is responsiveto the rotational inertia of the rotating article when the article isrotating in a forward direction and part of the retraction means isrotating a reverse direction so as to return the article to be rotatedto its support.

9. A vacuum deposition system comprising:

a vacuum chamber;

a deposition material source mounted in the vacuum chamber;

a substrate holder in the vacuum chamber;

support means in the vacuum chamber for supporting the substrate holder;and a mechanism in said vacuum chamber for suspending and rotating thesubstrate holder, said mechanism having;

a rotatable housing;

retraction means rotatable with said rotatable housing; and

releasable latch means engageable by rotation of said retraction meansfor coupling the substrate holder to said retraction means;

said retraction means being responsive to the inertia of the article tobe suspended when the rotatable housing is rotated so as to suspend thearticle prior to its being rotated, then rotate together with saidrotatable housing said first member and adapted for engagement with anarso that said mechanism and substrate holder rotate ticle having avelocity different from that of said rotating together. means.

10. A system as in claim wherein said releasable lat h 12. A mechanismas set forth in claim 11 wherein said first means comprises a latchmember and an engaging member; 5 member is a nut and said second memberis a screw adapted to and rotation of said retraction means brings thelatch and encooperatively engage Said gaging members im engagemem 13. Amechanism as set forth in claim 12 wherein said nut is 11 A i l rotationmechanism comprising; adapted to slide along the axis of said rotatingmeans.

14. A mechanism as set forth in claim 11 wherein said artirotatingmeans; and

l0 cle 1s a stationary article.

retraction means having a first member rotatable by said rotating meansand a second member threaded within

1. An article rotational mechanism comprising: rotatable retractionmeans responsive to the inertia of an article to be rotated to move thearticle to be rotated from an initial position, then to rotate thearticle, and means for coupling the article to be rotated to saidretraction means.
 2. The apparatus of claim 1 wherein the retractionmeans is a nut and screw which are constrained to rotate with respect toone another by the rotational inertia of the article to be rotated tomove the article to be rotated from the initial position, then whichrotate together to rotate the article.
 3. The apparatus of claim 1wherein said retraction means is responsive to the rotational inertia ofthe rotating article when the article is rotating in a forward directionand a portion of the rotatable retraction means is rotating in a reversedirection so as to return the article to its initial position.
 4. Theapparatus of claim 1 wherein said means for coupling the article to berotated to said retraction means is releasable and comprises a latchmember coupled to said retraction means and a means engageable with saidlatch member coupled to the article to be rotated.
 5. The apparatus ofclaim 1 additionally comprising: means tending to restrain theretraction of said rotatable retraction means.
 6. An article suspensionand rotation apparatus comprising: a rotatable housing; retractionmeans, responsive to the rotational inertia of an article to be rotatedwhich rests on a stationary support for the article from its support,Coupled to said rotatable housing; a latch member coupled to saidretraction means; and means, releasably engageable with said latchmember, coupled to the article to be rotated.
 7. The apparatus of claim6 wherein the retraction means is a nut and screw which are constrainedto rotate with respect to one another by the rotational inertia of thearticle to be rotated to move the article from its support, then rotatetogether to rotate the article.
 8. The apparatus of claim 7 wherein saidretraction means is responsive to the rotational inertia of the rotatingarticle when the article is rotating in a forward direction and part ofthe retraction means is rotating a reverse direction so as to return thearticle to be rotated to its support.
 9. A vacuum deposition systemcomprising: a vacuum chamber; a deposition material source mounted inthe vacuum chamber; a substrate holder in the vacuum chamber; supportmeans in the vacuum chamber for supporting the substrate holder; and amechanism in said vacuum chamber for suspending and rotating thesubstrate holder, said mechanism having; a rotatable housing; retractionmeans rotatable with said rotatable housing; and releasable latch meansengageable by rotation of said retraction means for coupling thesubstrate holder to said retraction means; said retraction means beingresponsive to the inertia of the article to be suspended when therotatable housing is rotated so as to suspend the article prior to itsbeing rotated, then rotate together with said rotatable housing so thatsaid mechanism and substrate holder rotate together.
 10. A system as inclaim 5 wherein said releasable latch means comprises a latch member andan engaging member; and rotation of said retraction means brings thelatch and engaging members into engagement.
 11. An article rotationmechanism comprising: rotating means; and retraction means having afirst member rotatable by said rotating means and a second memberthreaded within said first member and adapted for engagement with anarticle having a velocity different from that of said rotating means.12. A mechanism as set forth in claim 11 wherein said first member is anut and said second member is a screw adapted to cooperatively engagesaid nut.
 13. A mechanism as set forth in claim 12 wherein said nut isadapted to slide along the axis of said rotating means.
 14. A mechanismas set forth in claim 11 wherein said article is a stationary article.